A lysosomal enzyme involved in diphosphatidylglycerol degradation

A soluble lysosomal phosphodiesterase in rat liver that hydrolyzes monoacylglycerophosphorylglycerophosphorylglycerol (AGPGPGase) was shown to be distinct from a lysosomal acid phosphodiesterase IV (PDase IV) which catalyzes the hydrolysis of bis(p-nitrophenyl) phosphate. The criteria used to distinguish lysosomal AGPGPGase from PDase IV were: separation on ion exchange celluloses, dissimilar inhibition patterns and different rates of inactivation on concentration. The lysosomal PDase IV activity was competitively inhibited by inorganic phosphate with a Ki value of 0.33 mM phosphate and was inhibited by a number of organophosphoryl compounds including AGPGPG, phosphatidylcholine, phosphatidylinositol, ATP and 4-methylumbelliferylpyrophosphate.